Multi-layer polyphase winding member and transformer

ABSTRACT

Disclosed is a polyphase member for a position measuring transformer formed by multiple layers of printed circuit active and inactive conductors. The inactive conductors connect the active conductors to form winding sections and the winding sections are interconnected by printed circuit inactive conductors to form polyphase windings. Each layer includes groups of conductors including a predetermined number, usually an equal number, of active conductors of first and of second cofunction, e.g., sine or cosine, types. The winding sections are positioned with a specific phase relationship, such as quadrature, to a reference winding. The active conductors on each layer of the polyphase member are positioned such that a blank area called an active conductor void or gap, occurs where normally in a periodic configuration an active conductor would be positioned. Still further, the layers are complementary in that they are combined into a multi-layer member so that the active conductors on one layer are superposed the active conductor voids or gaps on another layer whereby the multi-layers as a whole present to the reference winding uniformly spaced active conductors.

[451 June 6, 1972 ABSTRACT Disclosed is a polyphase member for aposition measuring transformer formed by multiple layers of printedcircuit active and inactive conductors. The inactive conductors connectthe active conductors to form winding sections and the winding sectionsare interconnected by printed circuit inactive conductors to formpolyphase windings. Each layer includes groups of conductors including apredetermined number, usually an equal number, of active conductors offirst and of second cofunction, e.g., sine or cosine, types. The windingsections are positioned-with a specific phase relationship, such UnitedStates Patent Foster MEMBER TRANSFORMER [72] Inventor: Vincent F.Foster, New Rochelle, N.Y.

[73] Assignee: Inductosyn Corporation, New York, NY.

[22] Filed: May 13, 1970 [21] Appl. No.: 36,913

[54] MULTI-LAYER POLYPHASE WINDING as quadrature, to a referencewinding. The active conductors on each'layer of the polyphase member arepositioned such that a blank area called an active conductor void orgap, occurs where normally in a periodic configuration an activeconductor would be positioned. Still further, the layers arecomplementary in that they are combined into a multi-layer member sothat the active conductors on one layer are superposed the activeconductor voids or gaps on another layer whereby the multi-layers as awhole present to the reference winding uniformly spaced activeconductors.

12 Drawing Figures wm w 1/ 1 l 62 6 3.1 3 31 3 s0 H I m mm m w i, H .q 9S v n m m ..o 5, E E l T n .1 u d M A w .m% G P m ma m m m m m mm M U nm T do mddd Kd n A n. rnnn m n T ammmaa a m t S Tfmm 1 n e D FMFFFF a Ra E n mm N 940325 E "Um N 666666 m u U 999999 H I& HHHHHH .7. L 492 3 4W" d M Std 878485 n 8493 9 1 .3 .93 Wm 11] MMMWMM mm flaw n [.lf. l.332333 PA MULTI-LAYER POLYPHASE WINDING MEMBER AND TRANSFORMERBACKGROUND OF THE INVENTION This invention relates to position measuringtransformers of the type in which two relatively movable members areprovided, one having at least two planar windings (called polyphasewindings) which are phase shifted in space relative to each other andinductively coupled to another planar winding carrier by the othermember.

When one winding on one member is energized with an alternating primaryvoltage, the current in that winding induces a secondary voltage in anywinding on another member which happens to be in close proximitythereto.

In practice, position measuring transformers have employed on one membera single winding formed from uniformly spaced, series-connected activeconductors. That member is usually a single-phase member whichconventionally defines a .reference pitch, that is, defines a periodicspacing of the active conductors. In practice, for linear devices thesingle-phase member is called the scale and for rotary devices it iscalled the rotor.

The other relatively movable member of position measuring transformersgenerally includes two windings, each phaseshifted in space with respectto the other thereby presenting two different phases to the single-phasemember, and hence that other member is called the polyphase member.Conventionally, the polyphase member is called the slider in the case oflinear devices and the stator" in the case of rotary devices. While thepolyphase member (slider or stator) has windings which are phase-shiftedin space with respect to each other, those windings have a specificphase relationship to the single winding on the single-phase member(scale or rotor).

The phase-shift between the windings, called polyphase windings, on thepolyphase member is generally one quarter of the cycle of the winding onthe single-phase member. Accordingly, the phase shift between thepolyphase windings is a quadrature phase shift and hence is a phaseshift analogous to the quadrature phase shiftv between sine and cosinetrigonometric functions. When the polyphase windings are shifted aquarter cycle, they are, therefore, conventionally identified as thesine and cosine windings. While sine and cosine windings areconventional, other phase shifts, of course, may be implemented. Forexample, 120 shifts between each of three windings may be employed toform a three-phase system. Broadly, the term polyphase describes allsuch phase-shifted windings. Additionally, the term cofuction is alsogenerically used to describe the polyphase windings of positionmeasuring transformers since sine and cosine, for example, aretrigonometric cofunctions of the same angle.

Position measuring transformers of the above type have been known andused for many years. For example, the U.S. Pat. No. 2,799,835 to R. W.Tripp et al., discloses a transformer of the above type employing planarwindings. Although the improvements disclosed in the Tripp et al.,patent resulted in a more accurate transformer, some embodiments of thelatter are difficult to manufacture, particularly because the intricatewiring patterns of polyphase windings have required large numbers ofsoldered or welded wire connections. For example, in order to properlyconnect the various active conductors comprising the windings, i.e.,those conductors extending transversely of the direction of relativemovement of themembers, a hole must be drilled in the supporting memberof glass or the like adjacent each conductor group and connector wirespassed through the holes and soldered or welded to the conductors. In atypical case, wherein the polyphase winding support member comprises 24conductor groups, 24 holes, 48 wires and 48 soldered or welded wireconnections would be required.

Improvements to the polyphase member of position measuring transformersare disclosed in U.S. Pat. Nos. 2,915,722 and 2,924,798 to Vincent F.Foster. Briefly, the U.S. Pat. No.

2,915,722 patent teaches reducing unwanted components of induced voltageby providing first and second polyphase windings on the slider which arephysically located symmetrically with respect to a common center line.The U.S. Pat. No. 2,924,798 adds the additional improvement ofinterwiring first and second cofunction winding sections in a setsequence thereby reducing unwanted induced voltages in the secondary.

While the improvements in sliders represented by the U.S. Pat. Nos.2,915,722 and 2,924,798 have resulted in significantly better operationof the position measuring transformers of which they form a part, theseimprovements have not eliminated the complex nature of sliders or otherpolyphase members and particularly have not eliminated intricate wiringpatterns which exhibit large numbers of wire crossings and so]- deredconnections.

Later developments, such as those disclosed and claimed in the U.S. Pat.No. 3,441,888 to C. L. Farrand, have attempted to further improve andsimplify the construction of such measuring transformers. The latterpatent discloses multiple layer planar windings wherein sine and cosineconductor groups are staggered with respect to sine and cosine conductorgroups on another layer. Although an increase in accuracy and otherbenefits are attained by this arrangement, the assembly of the variousconductor groups still necessitates a considerable number of wiredconnections between different conductor groups in the different layers.The nature of such connections, because of their cross wirerelationship, still necessitates a considerable number of soldered orwelded connections which, in many cases, must be done by hand. Thisconsiderable number may reduce the reliability of the transformer.

SUMMARY OF THE INVENTION The present invention is a polyphase windingmember and winding arrangement for a position measuring transformerwhich requires far fewer soldered or welded wire connections, than isrequired by prior art transformers of this type. Specifically, in oneembodiment only two such connections, other than the necessaryterminals, are required regardless of the number of groups of activeconductors employed. Thus, the resulting transformer requires less laborto manufacture and effects a significant increase in reliability.

The polyphase member of the present invention includes multiple layersof active conductors. Groups of the active conductors are connected byinactive conductors to form winding sections and the winding sectionsare interconnected to form polyphase windings. Each layer includes apredetermined number, usually an equal number, of active conductors offirst and of second cofunction types. The winding sections arepositioned with a specific phase relationship to a reference winding.That reference winding is typically a single-phase winding on astationary member of a position measuring transformer. Further, theactive conductors on each layer of the polyphase member are positionedsuch that there occurs a void, that is, a space or gap characterized bythe absence of one or more active conductors where normally in aperiodic configuration complementary active conductor or conductorswould be located. Still further, the layers are combined into amultilayer member so that the active conductors on one layer arepositioned opposite active conductor voids on another layer. Themulti-layer member thus formed typically includes a plurality ofinterdigitated cofunction winding sections.

The groups of active conductors forming winding sections in differentlayers have groupings and spacial relations such that they are connectedby inactive conductors lying in the same layers but generally having nomagnetic inductive relation thereto so that the active conductors andtheir connecting inactive conductors are all formed mainly by printedcircuit techniques.

Also, according to the present invention, one layer contains a patternof interspaced groups of active conductors of one significance, e.g.,sine, and groups of active conductors of another significance, e. g.,cosine, while another layer contains a complementary and overlyingpattern of such groups to form an array of interspaced groups of the twosignificances, with as few as a pair of circuit connections extendingbetween the layers to connect the groups of similar significance.

Further, the particular arrangement of the groups of active conductorsand their connecting inactive conductors enables such groups to besymmetrically arranged about a center line to reduce unwanted componentsof induced voltages while maintaining the inactive conductors generallyout of magnetic inductive relation to such groups.

A further feature of the invention is the arrangement wherein theinactive conductors connecting active conductors in one layer arelocated in inductive coupling relation to the inactive conductorsconnecting active conductors in another layer such as to reduce orcancel the undesired one-tum loop coupling which would otherwise occur.

A still further feature of the invention is the arrangement of an arrayof winding sections formed by groups of active conductorscertain ofwhich are connected by inactive conductors in the same layer leading toone margin or marginal area of the array and others of which areconnected by inactive conductors in the same layer leading to theopposite margin or marginal area of the array. By providing two layersof such winding sections, four such margins are provided for locatingthe connecting inactive conductors to eliminate wire cross-over points.

A still further feature of the invention which enables attainment of theabove results is that groups of active conductors have one activeconductor located in one layer and another active conductor located inanother layer.

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1(a) is an enlarged plan view of aslider wherein the sine and cosine windings are arranged in two layers,each layer consisting of a printed circuit which includes both activeconductors, which are generally the transverse conductor portions, andinactive conductors, which are generally the longitudinal conductorportions, the active conductors and inactive conductors in fulllines-consisting of a printed circuit in one layer, the activeconductors and inactive conductors appearing in broken lines appearingin another layer. 7

FIG. 1(b) depicts a schematic plan view of a single-phase referencewinding, having active conductors defining a reference pitch, whichreference winding is relatively movable with respect to the polyphasemember of FIG. 1(a) to which it is inductively coupled.

FIG. 1(0) depicts a schematic plan view of the winding like that of FIG.1(b) but shifted in space one-quarter cycle with respect to the FIG.1(b) position.

FIG. 2(a) depicts an enlarged plan view of an upper layer, having 24active conductors, of a polyphase member comprised of 48 activeconductors.

' FIG. 2(b) depicts an enlarged plan view of the lower layer, having 24active conductors, of a polyphase member having an upper layer like thatdepicted in FIG. 2(a).

FIG. 2(0) depicts a portion of a reference winding positioned to showits relative size with respect to the FIG. 2(a) sections.

F IG. 3 depicts a front view of a portion of the FIG. 2(a) and FIG. 2(b)layers superposed but drawn slightly offset to show their overlayposition and with the bottom layer shown dotted.

FIG. 4 depicts a cross-Sectional end view of a position measuringtransformer having a polyphase member positioned, with a gap, over asingle-phase member.

FIG. 5 depicts a rotary embodiment, patterned after FIG. 1(a), of apolyphase member of the present invention.

FIG. 6(a) and FIG. 6(b) depict alternate embodiments of upper and lowerlayers, respectively, similar to the layers of FIG. 2(a) and FIG. 2(b).

FIG. 7 depicts the layers of FIG. 6(a) and FIG. 6(b) overlaid on a baseto form a polyphase winding member and depicts that polyphase windingmember above a single-phase winding member where the latter has activeconductors longer than the active conductors of the former.

DETAILED DESCRIPTION FIG. 1(a) depicts apolyphase member havingpolyphase (also called cofunction) windings in the form of a sinewinding 18 and a cosine winding 19. The sine winding 18 is connectedbetween terminals 20 and 21 and the cosine winding 19 is connectedbetween terminals 23 and 24. Both the sine and cosine windings l8 and 19are comprised of a plurality of winding sections, numbered left to rightfrom 1 to 16. Some of the winding sections are on one layer 47 and someare on another layer 48 and some are on both. Since FIG. 1(a) is a topview and in schematic form, the layers 47 and 48 are not observable assuch therein but are shown and described in connection with FIGS. 2, 3and 4 hereinafter. The layers 47 and 48 are separated by an insulatorlayer 49.

In FIG. 1(a), the sine winding 18 is comprised of winding sections 1, 3,5, 7, 10, l2, l4 and 16 and the cosine winding 19 is comprised ofwinding sections 2, 4, 6, 8, 9, l1, l3 and 15. Winding sections 4, 5,8,9, 10, 13 and 14 are in one layer and winding sections 2, 3, 6, 7, l1and 12 are in the other. Winding sections 1 and 16 are formed by activeconductors from each layer. The winding sections, or more simplysections, and other conductors, such as inactive conductor 36 betweensections 11 and 15, which appear on layer 48 are represented by solidlines. In order to distinguish layers, the sections and otherconductors, such as inactive conductor 35 between sections 9 and 13,appearing on the layer 47 are shown as broken lines.

Each winding section for the polyphase member of FIG. 1(a) includes twoactive conductors 27 and 28. Each of the active conductors 27 and 28 isgiven a prefix corresponding to the appropriate winding section. Forexample, the active conductors for section 2 are designated as 227 and2-28. Each of the active conductors 27 and 28 for the 16 sections ofFIG. 1(a) terminates with an end in one direction forming a first uppermargin on insulator 49 and terminates with an end in an opposite seconddirection forming a second lower margin on insulator 49. Each of theconductors 27 and 28 is connected on its ends by an inactive conductor30 where again the particular inactive conductor is prefixed with theappropriate corresponding section number. For example, section 2 hasactive conductor 228 connected along the upper margin 33 to activeconductor 2-27 by the inactive conductor 230. Most of the sections ofFIG. 1(a) have section openings 31 along one margin opposite inactiveconductors -30 along the opposite margin where the prefix notation isagain employed. For example, section 2 has a section opening 2-31 alongthe bottom margin 34 opposite the inactive conductor 230.

In FIG. 1(a) winding section 16 does not include an inactive conductor30 and the active conductors 16-27 and 16-28 are on different layers.With the active conductors on different layers and no inactiveconductor, terminals 20 and 21 are readily located along margin 34rather than along margin 33 so that winding section 16 provides for anacross-the-winding placement of those terminals. If opening 16-32 werereplaced by an inactive conductor 16-30 (not shown) connecting theinactive conductors 16-27 and 16-28, then terminals 20 and 21 would betypically positioned along margin 33 shown, for example, as alternateterminals 20' and 21'. When an inactive conductor 16-30 is provided inplace of terminals 20 and 21, the inactive conductor portion 26 betweenterminals 20 and 21 is, of course, removed.

While winding section 16 provides for across-the-winding placement ofterminals 20 and 21, winding section 1, with opening l-32, analogouslyprovides for across-the-winding placement of interconnecting tabs 37 and38. The across-thewinding placements achieved with sections 1 and 16allows all of the terminals (20, 21, 23, 24) and interconnection tabs(37, 38, 60, 61) to be located along margin 34 with none along margin33. This'single margin location is useful in preventing those tabs andterminals from coupling to the terminals of the single-phase windingplaced on the opposite margin as shown in FIG. 7.

The active conductors 27 and 28, such as 2-27 and 2-28, of FIG. 1(a) areincluded in winding sections which appear, also referring to FIG. l(b),at selected intervals 50 of a first plurality of periodic intervals 51and at selected intervals 54 of a second plurality of periodic intervals55. The periodic spacing of the winding sections 1 through 16 of FIG.1(a) can best be explained with respect to a reference. The reference istypically a single-phase winding of a position measuring transformerlike that schematically shown in FIG. l(b).

FIG. l(b) depicts a continuous winding 39 which is connected betweenterminals 40 and 41. Continuous winding 39 is comprised of a pluralityof periodic, parallel, series-connected active conductors 43. The activeconductors 43 are connected at their terminations along the top byinactive conductors 45 and at their termination along the bottom byconductors 46. Active conductors 43 are spaced periodically at adistance P and therefore are said to have a pitch of P. The continuouswinding 39 is cyclic over each distance of 2P, that is, P is a halfcycle of the reference.

The spacing of the winding sections of FIG. 1(a), relative to thecontinuous winding 39 as a reference, is such that winding sections 1,3, 5, 7, 10, 12, 14 and 16, which form the sine winding 18, are centeredat selected intervals 50 associated with the first plurality of periodicintervals 51. The first plurality of periodic intervals 51 appear everyhalf cycle, P, of continuous winding 39, as shown for example withreference to FIG. 1(b), at the midpoints of each of the inactiveconductors 45 and 46.

The winding sections 2, 4, 6, 8, 9, 11, 13, and 15 forming the cosinewinding 19 in FIG. 1(a), appear at selected intervals 54 of the secondplurality of periodic intervals 55. The second plurality of periodicintervals 55 is phase-shifted from thefirst plurality of periodicintervals 51 one-quarter of a cycle, 2P)/4, of continuous winding 39.

1 In order to obtain the desired quadrature relationship between sinewinding 18 and cosine winding 19, the individual winding sections 1through 16 are spaced at periodic intervals which have a quadraturerelationship, namely, spaced at the first plurality of periodicintervals 51 or at the quarter-cycleshifted second plurality of periodicintervals 55. While the winding sections for sine winding l8 may beplaced at any of the periodic intervals 51 and the winding sections forcosine winding 19 may be placed at any of the periodic intervals 55, thespacing at the selected intervals 50 and 54, respectively, of FIG. 1 istypical.

The section spacing, C, between the central two sections, sections 8 and9, is typically selected equal to n"P in accordance with theabove-referenced Foster US. Pat. No. 2,915,722. where n equals the evennumber of active conductors per section and P is the referencehalf-cycle. Selecting C in that manner insures that the sine and cosinewindings 18 and 19 of FIG. 1(a) will each have their equal number ofwinding sections symmetrically located with respect to a center linerunning between sections 8 and 9.

FIG. 2(a) depicts the upper of two layers of a multi-layer, polyphasemember in accordance with the present invention. FIGS. 2(a) and 2(b) aredrawn to a scale of approximately 1 times actual size for a slider inaccordance with one preferred embodiment of the present invention. FIG.2(b) depicts the lower layer used in cooperation with the upper layer ofFIG. 2(a).-The layers of FIGS. 2(a) and 2(b) are designed with centerspacing C of the order of 0.2000 inches, the spacing p between activeconductors of the order of 0.0333 inches, and the section spacing, S, ofthe order of 0. l5 inches. Additionally, the width b, of a typicalactive conductor 3-58(a is approximately one-third p or 0.011 inches.Accordingly, the gap, .s," between active conductors equals p minus b oralternatively, 11" equals 2 s.

The upper layer 66 depicted in FIG. 2(a) consists of 24 activeconductors, like typical active conductor 3-58(a), which individuallyform at least portions of the winding sections 101, 103, 104, 107, 108,111, 112, 113, 116, 117, 120, 121 and 124. The active conductors areidentified by the prefix notation like that previously employed.interspersed between the winding sections are a plurality of windingsection voids, that is gaps or blank spaces where, in a periodicconfiguration, a winding section would normally occur. Particularly,winding section voids occur between winding sections 101 and 103, 104and 107, 108 and 111, 113 and 116, 117 and 120, and 121 and 124.

In a similar manner, the lower layer 67 of FIG. 2(b) includes at leastportions of winding sections 101, 102, 105, 106, 109, 110, 114, ,115,118, 119, 122, 123 and 124. In FIG. 2(b), winding section voids areinterspersed between winding sections 102 and 105, 106 and 109, and 114,and 118, 1 19 and 122.

The winding sections 101 and 124 are formed by active conductors l58(a),l58(b), 24-58(a and 24-58(b) from each of the FIG. 2(a) and FIG. 2(b)layers. The active conductors on each layer for winding sections 101 and124 overlay active conductor voids on the other layer. Moreparticularly, winding section 101 is formed by an active conductorl58(a) in upper layer 66 together with the active conductor l58(b) fromthe lower layer 67. Similarly, active conductor 24-58(a) is in upperlayer 66 and active conductor 24-58( b) is in lower layer 67 andtogether they fonn winding section 124.

In order to provide for a through-layer connection, active conductorl58(a) terminates in a tab and active conductor l58(b) terminates in atab 140'. A second through-layer connection is provided for betweenwinding section 121 and winding section 123 by tabs 141 and 141.

When the layers of FIGS. 2(a) and 2(b) are superposed (as partiallyshown in FIG. 3), the tabs 140 and 141 are connected to the tabs 140 and141, respectively, in any conventional manner so as to make athrough-layer connection. For example, a hole 70 is drilled through theupper layer tab 140 allowing a soldered connection 71 to be made throughto the lower layer tab 140'.

FIG. 3 depicts a portion of the upper layer 66 of FIG. 2(a) superposedover a portion of the lower layer 67 of FIG. 2(b), with the layers drawnslightly shifted from their actual position so that the lower layer maybe seen in the drawings. Although not shown exactly superposed, theinactive conductor 74 on layer 66, connecting winding section 101 towinding section 103, is intended to be identically superposed overinactive conductor 75 connecting winding section 101 to winding section105. In a similar manner, inactive conductor 77 from winding section 104is intended to be identically superposed over a portion of inactiveconductor 78 from winding section 102. The purpose of superposing theinactive conductors from layer to layer is to reduce the unwantedcoupling which might otherwise be generated by inactive conductors.Besides superposing, the inactive conductors generally must be connectedsuch that they carry current in opposite directions. For example, themagnetic field generated by a current through inactive conductor 74 iseffectively cancelled by the equal but opposite current through inactiveconductor 75. It is evident that current is equal and opposite becauseactive conductors l58(a and l58(b) are series-connected by athrough-layer connection 71 between tabs 140 and 140. Inspection ofFIGS. 2(a) and 2(b) in conjunction with the partial view in FIG. 3reveals a similar equal but opposite current relationship between mostof the superposed inactive conductors of the upper layer 66 and thelower layer 67. As a further example, the equal but opposite currentrelationship exists between the superposed inactive conductors 77 and78.

It is also apparent from FIG. 3, in accordance with the presentinvention, that the winding sections on one of the two layers of FIG. 3are positioned in the winding section voids of the other layer in FIG.3. For example, winding sections 103 and 104 on the upper layer 66 arepositioned in the winding section voids appearing between the windingsections 102 and 105 on the lower layer 67. Similarly, the windingsection 102 and the active conductor 1-58(b) appearing on the lowerlayer 67 are positioned'in the winding section voids between windingsection 103 and active conductor 1-58(a) on the upper layer 66. The termsuperposedwith has a meaning which is generic to and covers theterms"positioned in" as used in this paragraph and the terms opposite,superposed over and superposed" as used in other parts of thespecification without regard to whether an upper layer or a lower layeris intended.

When the upper layer 66 and the lower layer 67 are superposed as shownin FIG. 3 and the tabs 140 and 140 (and also tabs 141 and 141' not shownin FIG. 3) are connected with a through-layer connection 71 asindicated, continuous sine and cosine windings are formed. The sinewinding terminates in tab 84 on the upper layer 66 and tab 83 on lowerlayer 67. The continuous cosine winding similarly terminates in tab 82on upper layer 66 and tab 81 on lower layer 67. In a manner analogous tothe interconnection of tabs 140 and 140', the tabs 81, 82, 83 and 84 maybe interconnected with the tabs 81', 82, 83, and 84, respectively, inorder to provide for external connections to the windings at outsidepoints.

With the through-layer connection of tabs as indicated above, the sinewinding is comprised of sections 101, 103, 105, 107, 109, 111, 114, 116,118, 120, 122 and 124. Similarly, the cosine winding is comprised ofwinding sections 102, 104, 106, 108, 110, 112, 113, 115, 117, 119, 121and 123. It is apparent that a composite winding including an upperlayer 66 and a lower layer 67 includes interdigitated sine and cosinesections in which there are an equal number of active conductors on eachlayer and further in which on each layer there is the same number ofactive conductors associated with sine winding sections as with cosinewinding sections.

In accordance with the present invention, the superposed printed layersin FIG. 3 have complementary arrays of active conductors which whenviewed as a composite provide uniformly spaced active conductors of sineand cosine significance. Furthermore, the interdigitation of the sineand cosine winding sections is reversed at winding sections 112 and 113thereby incorporating the teaching of the aboveidentified U.S. Pat. No.2,915,722 patent.

Because of the symmetry provided by having an equal number of activeconductors per layer, by having the same number of active conductors insections associated with the sine winding as with the cosine winding oneach layer, and by having interdigitated winding sections, the exactnesswith which the layers must be superposed during the manufacturingprocess is reduced. Shifts of one layer with respect to the other layerare tolerable because the unwanted induced voltages caused by suchshifts tend to cancel each other. These unwanted voltages aresubstantially eliminated by equal but opposite signals induced in eachof the sine and cosine windings which effects tend to cancel each other.For example, current entering terminal 81' of FIG. 2( b) travels fromright-to-left along inactive conductor 78 and through each of thesections 102, 106, 110, 115, 119, and 123 to tab 141. When the layer ofFIG. 2(a) is superposed over the layer of FIG. 2(b), as shown in part inFIG. 3, tab 141 is connected to tab 141 so that the current introducedin terminal 81' travels through sections 121, 117, 113, 112, 108 and 124thereafter returning left-to-right along inactive conductor 77 toterminal 82. Cancellation occurs, for example, between superposedinactive conductors 77 and 78 which have equal but opposite currentsasexplained above.

Referring to FIG. 2(0), a portion of a single-phase winding 126 is showntypically depicting its relative size and position with respect to thewinding sections of a polyphase winding such as shown in FIG. 2(a). Onlya portion of a single-phase winding 126 is shown since that winding istypically of greater length usually extending beneath the windingsection 101 all the way to the winding section 124 and beyond.

FIG. 4 depicts a side view of a polyphase, multi-layer member 149positioned above a single-phase member 151.

The member 149 typically consists of a base 144 comprised of arelatively thick rigid material such as metal or glass. Bonded to thebase 144 with an adhesive layer is a first insulated layer 67',corresponding to the lower layer 67 of FIG. 2(b). The layer 67' iscomprised of an insulating material 67'(a) such as Mylar clad to theconducting layer 67'(b), the latter of which includes the windingsections, tabs, and other conductors generally depicted in FIG. 2(b).

Bonded to the insulated layer 67 by adhesive layer 146 is the insulatedlayer 66 corresponding to the upper layer 66 of FIG. 2(a). The insulatedlayer 66, like the insulated layer 67, is further comprised of aninsulating material 66(a) clad to the conducting layer 66(b), the latterof which includes the winding sections, tabs, and other active andinactive conductors generally depicted in FIG. 2(a).

Bonded to the insulated layer 66 by adhesive layer 147 is the insulatedlayer 68 which serves as an electro-static shield. Insulated layer 68 iscomprised of an insulator 68(a) clad to a conducting sheet 68(b), wherethe latter is a conductor such as aluminum foil. Insulated layer 68 isof the type described in U.S. Pat. No. 3,090,934 to C. L. Farrand.

The base 144 and the attached layers 145, 67', 146, 66, 147 and 68comprise a first member including first (66') and second (67) insulatedlayers of cofunction windings wherein each of the layers 66 and 67'includes a substantially equal number of winding sections of first andof second cofunction types as explained in connection with FIGS. 2(a)and 2(b). Further, each of the insulated layers 66 and 67' arepositioned so that the active conductors and winding sections on one ofthe layers are superposed over the active conductor voids and windingsection voids on the other layer.

The member 149 is positioned in close proximity to a member 151. Themembers 149 and 151 are separated by an air gap 150. The member 151 iscomprised of a base 154 typically made of glass or metal. A suitablemetal base is described in U.S. Pat. No. 3,202,948 to C. L. Farrand.Bonded to the base 154 by an adhesive layer 128 is an insulated layer126'. The insulated layer 126' is comprised of an insulator 126(a) cladto a conducting layer 126(b), the latter of which is formed into a scalelike the single-phase winding 126 depicted in FIG. 2(a).

The member 149 and the member 151 are mounted relatively movable withrespect to each other and further, the windings of the insulated layers66', 67, and 126 are inductively coupled to each other.

Although a wide variance in dimensions is possible, typical dimensionsfor the bases and layers of FIG. 4 are presented in the following CHARTI.

CHART I Reference No. Dimension (Inches) 144 0.365 145 0.0005 67 (a)0.002 67' (b) 0.001 146 0.0005 66' (a) 0.002 66 (b) 0.001 147 0.000568(a) 0.001 68(b) 0.001 150 (air gap) 0.005 126' (b) 0.001 126 (a) 0.002128 0.0005 154 0.365

OPERATION The function of the position measuring transformers previouslydescribed with reference to FIGS. 1(a), 1(b), 2(a), 2(b), 3, and 4 is tomeasure or indicate the relative position of two members. The twomembers are generally rigidly attached to relatively movable parts (notshown) of an apparatus such as a machine tool and therefore areoperative to indicate the relative positions of the parts of thatmachine tool.

In order to measure relative position, the position measuringtransformer schematically shown in FIGS. 1(a) and 1(b) has a signalapplied between terminals 40 and 41 of the continuous winding 39 of FIG.1(b). For such a signal applied between terminals 40 and 41, in themember of FIG. 1(b), a maximum signal is induced in the FIG. 1(a) sinewinding 18 and a minimum signal is induced in the FIG. 1(a) cosinewinding 19. The maximum signal is induced in sine winding 18 becauseeach of the active conductors 27 and 28 for each winding section of thesine winding 18 is symmetrically positioned between two parallel activeconductors 43 of continuous winding 39 so that the induced voltages ineach of the active conductors 27 and 28 are equal and additive.

By way of comparison, each of the active conductors 27 and 28 of thewinding sections for the cosine winding 19 are positioned such that theysymmetrically straddle a single active conductor 43 of the continuouswinding 39 so that the voltages induced in the active conductors 27 and28 are equal but opposite so as to tend to cancel each other and producea minimum signal.

In FIG. 1(c), the continuous winding 39 is shifted relative to the sinewinding 18 and the cosine winding 19 of FIG. 1(a) as compared with theposition of the continuous winding 39 of FIG. 1( b). This shift ofcontinuous winding 39 is analogous to a shift of continuous winding 39of FIG. 1(b) an amount equal to a quarter cycle of continuous winding 39such as would occur if continuous winding 39 were attached to a movingpart of a machine tool.

For a current in continuous winding 39' of FIG. 1(0) between terminals41 and 40', the signal induced between terminals 20 and 21 for sinewinding 18 is a minimum and the signal induced between terminals 23 and24 for cosine winding 19 is a maximum.

When the continuous winding 39 of FIG. 1(b) is shifted to positionsbetween that shown in FIG. 1(b) and that shown in FIG. 1(c), then themagnitude of the signals detected at terminals 23 and 24 and terminals20 and 21 vary proportionately. For example, when the continuouswinding39 is half-way between the FIG. 1(b) position and the FIG. 1(c)position, the signals at terminals 23 and 24 and terminals 20 and 21 areequal. As is well known in the prior art, unique signals are generatedfor all relative positions of the polyphase and singlephase windingsover each cycle.

While the above-described operation is typical when position measuringtransformers are used as transmitters, position measuring transformersare also frequently used as receivers. As a receiver the transformer ofFIGS. 1(a) and 1(b) may have in-phase, sinusoidal signals appliedbetween terminals 23 and 24 and between terminals 20 and 21. Forselectable magnitudes of those input signals, a corresponding sinusoidalerror signal having a magnitude which is a function of the relativeposition of the FIG. 1(a) and FIG. 1(b) members is generated betweenterminals 40 and 41.

FURTHER AND OTHER EMBODIMENTS FIG. depicts a rotary embodiment of amulti-layered, l6- section, polyphase, and specifically two-phase,member 218. The member 218 includes winding sections 201, 202, 216.

' Those winding sections are connected into a sine winding 220comprising winding sections 201, 203, 205,207, 209, 211, 213, and 215and into a cosine winding 221 comprising winding sections 202, 204, 206,208, 210, 212, 214, and 216. Similar to the convention employed withrespect to FIG. 1(a) and FIG. 3, the winding sections, activeconductors, and inactive conductors appearing on one layer are shown assolid lines while the similar components appearing on the other layerare shown by broken lines. For example, active conductor 225, of windingsection 215, inactive conductor 226, connecting active conductor 225 tothe winding section 201, and winding section 201 itself, are all on onelayer. In a similar manner, active conductor 228 of winding section 215and inactive conductor 229 connecting the active conductor 228 to thewinding section 203, and the winding section 203 are all on anotherlayer.

The cutaway view through portions of winding sections 212, 213, 214,215, and 216 reveals a portion of a single-phase member 232 including acontinuous, single-phase winding 231. The winding 231 is comprised of aplurality of radially extending, equally spaced, serially connectedactive conductors 233. The active conductors 233 have a pitch, P, whichin the case of a rotary device is an angular measurement between activeconductors. Note that in connection with FIG. 1(b), the pitch, P, wasmeasured in linear distance. The winding sections of the polyphasemember 218 are oriented with section spacing, S, which is apredetermined quantity with respect to the pitch, P, of the activeconductors on a single-phase member 232. In the case of FIG. 5, S equals1 A P. Therefore, a quadrature relationship exists between the sinewinding 220 and the cosine winding 221. As discussed above in connectionwith FIGS. 1(a), 1(b) and 1(0), other spacings may be employed toachieve difierent phase relationships between the polyphase windings andthe single-phase winding.

It should be noted in connection with FIG. 5 that winding sectionsassociated with the sine winding 220 are interdigitated with windingsections associated with the cosine winding 221. Similarly, an equalnumber of active conductors associated with the sine winding 220 appearon one layer 223 (broken) as on the other layer 224 (solid) andsimilarly, an equal number of active conductors associated with thecosine winding 221 appear on each of the layers 223 and 224.Furthermore, the two layers in the polyphase member 218 have activeconductors and winding sections which are superposed so that they falladjacent the active conductor voids and winding section voids on theother layers.

In order to connect the sections on the layers of the same cofunctionstype, tabs 239 and 240 are provided on layer 224 and tabs 239 and 240are provided on layer 223. A solder or other type electrical connectionmay then be made between tabs 239 and 239' and between 240 and 240'.Similarly, the terminals 243 and 244 for sine winding 220 and terminals246 and 247 for'the cosine winding 221 may include provision forthrough-layer connections.

FIGS. 6(a) and 6(b) depict upper layer 366 and lower layer 367,respectively, similar to the layers depicted in FIGS. 2(a) and 2(b). Thelayers of FIG. 6(a) and FIG. 6(b) differ from those of FIGS. 2(a) and2(b) in that they are without large tabs for through-layer connectionsand the inactive conductors interconnecting the active conductors aresymmetrically placed. More particularly, typical active conductors 357,357', 357" and 357" in FIG. 6 are analogous to the active conductors 58in FIGS. 2(a) and 2(b). Similarly, the end active conductors 358(a) and358'(a) on upper layer 366 and the end active conductors 358(b) and358(b) are similar to the end active conductors in FIGS. 2(a) and 2(b).The active conductors 358(a) and 358( b) do not terminate, however, in alarge tab but instead terminate in an inactive conductor 359(a) and359(b) which also are employed to make a through-layer connection. In asimilar manner, the active conductor 361 in upper layer 366 does notterminate in a large tab (like tab 141 in FIG. 2(a)) but merely extendslong enough to overlay the end of active conductor 358 in the lowerlayer 367, when the upper layer 366 is overlayed that lower layer 367.The reason that the tabs and other irregularities in the inactiveconductors of FIG. 2(a) and 2(b) have been eliminated in the FIG. 6embodiment is apparent after reference to FIG. 7.

In FIG. 7, the relatively movable member 325 includes a polyphasewinding 328, comprised of the upper layer 366 of FIG. 6(a) and the lowerlayer 367 of 6(b), mounted on the underside of a base 320. The member325 is depicted showing its position above a relatively movable member332. The member 332 includes single-phase winding 326 having activeconductors like typical active conductors 330, 330 and 330 which aregreater in length than the typical active conductors 357 357 and so onof the polyphase windings 328. Since the active conductors such astypical active conductor 330 are greater in length, it is important thatno unwanted conductor area be provided by polyphase windings 328 whichwould inductively couple those active conductors since any such areawould generate unwanted error signals. The polyphase member 325 havingpolyphase windings 328 is absent tabs and other irregularities andtherefore does not generate unwanted error signals. Additionally,polyphase windings 328 may be used with the single-phase winding 126 ofFIG.'2(c) where the active conductors 351 are shorter than the activeconductors of FIG. 7. Polyphase members comprised of layers like thoseshown in FIGS. 2(a) and 2(b), however, are not desirably used withmembers having active conductors of a length like that of activeconductor 330, which length is shorter than the length of activeconductors 58 in FIG. 2(a) and 2(b), because of the unwanted tab andother uncompensated conductive areas from which unwanted inductivecoupling is likely to result.

While the winding sections in all of the polyphase windings described inconnection with all of the embodiments herebefore have been depicted asincluding two coupling conductors per section, any number of couplingconductors per section may be employed within the spirit of the presentinvention. Accordingly, for the purposes of this specification, the termwinding section or more simply section" is defined to mean a portion ofa transformer winding which, when interconnected with other sections,forms a complete transformer winding. Sections are generally comprisedof one or more active conductors physically disposed on a member sothat, when another member is positioned in close proximity thereto,those active conductors inductively couple active conductors on thatother member. When there are two active conductors per section, thesections are frequently called U bar sections. When there are fouractive conductors per section, the sections are frequently called W barsections.

The W bar sections, of course, include two central active conductors andtwo outside active conductors totalling four active conductors.Referring to FIG. 1(a). for example, each of the sections 1 through 16can be replaced by W bar sections. In making that replacement, thesection spacing, S, is conveniently measured from a line equally spacedbetween the two central active conductors of the W bar sections.

With a substitution of the W bar or other type sections for the U barsections of FIG. 1(a), it should be noted that acrossthe-windingplacement of terminals or tabs from top to bottom margins are achievedby placing the active conductors of a single section on different layersin the same manner as acrossthe-winding placements were achieved withwinding section 1 and winding section 16 of FIG. 1(a) as previouslydiscussed More particularly, a W bar section is essentially two U barsections. Therefore, any one of the component U- bar sections within a Wbar section may be formed with an active conductor from each layer inthe same manner as the winding sections 1 and 16 of FIG. 1(a). Byforming sections with active conductors on different layers,across-the-winding connections are readily made.

While FIG. 4 depicts one multi-layer member, the present invention alsoencompasses many different variations. For example, the insulated layers66' and 67' in FIG. 4, have been indicated as comprised of conductinglayers 66 (b) and 67' (b) each clad to an insulated layer 66 (a) and 67(a), respectively. Alternatively, one single insulated layer such asMylar or other plastic may be employed with a conducting layer clad toeither side thereof. Other similar variations are, of course, possible.

While the invention generally includes active conductors superposed overactive conductor voids in a multi-layered structure, the activeconductor voids may actually be filled with conductors which areidentical to active conductors except that they are not connected onboth ends and accordingly cannot conduct electricity. These unconnectedconductors may be useful as mechanical supports without affecting theelectrical characteristics of the position measuring transformer.

Although the invention has been described with respect to a-c signalsand electromagnetic energy transfers (transformer action), the inventionalso encompasses d-c energization and/or electrostatic energy transfers(capacitor action).

While the invention has been particularly shown and described withreference to preferred embodiments thereof it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and the scope of theinvention.

What is claimed is:

1. A position measuring device comprising, a first relatively movablemember including first and second layers of cofunction windings whereineach layer includes a substantially equal number of active conductorsforming winding sections of first and of second cofunction types,wherein each layer includes winding sections separated by windingsection voids, said voids in each layer being characterized by theabsence of active conductors, and wherein said first layer is superposedover said second layer so that each winding section on each layer issuperposed with a correspondingwinding section void on the other layer,and

a second relatively movable member having a winding electrically relatedto said cofunction windings.

2. A winding member for a position measuring transformer comprisingfirst and second layers of cofunction windings, each of said layersincluding a substantially equal number of active conductors, said activeconductors forming winding sections of first and of'second cofunctiontypes, each of said layers including active conductors separated byactive conductor voids, said voids ineach layer characterized by theabsence of active conductors, wherein said first layer is superposedover said second layer so that each winding section on each layer issuperposed with a corresponding winding section void on the other layer.

3. The member of claim 2 wherein at least some of said winding sectionsare formed with active conductors from each of said layers. g

4. The member of claim 2 wherein said active conductors are printed onan insulated layer and wherein said active conductors are connected intowinding sections by printed inactive conductors.

5. The member of claim 2 wherein the number of active conductors formingsaid winding sections of said first cofunction type equals the number ofactive conductors forming said winding sections of said secondcofunction type.

6. A winding member for a position measuring transformer comprising, i

a first layer having first active conductors connected to form firstwinding sections appearing substantially at selected intervals of afirst plurality of periodic intervals and having second active'conductors connected to form second winding sections appearingsubstantially at selected intervals of a second plurality of periodicinterv vals, at least some of said first and second active conductorsseparated by active conductor voids,

- a second layer having third active conductors connected to form thirdwinding sections appearing substantially at selected intervals of saidfirst plurality of periodic intervals and having fourth activeconductors connected to form fourth winding sections appearingsubstantially at selected intervals of said secondplurality of periodicintervals, at least some of said third and fourth active conductorsseparated by active conductor voids, said first, second, third, andfourth winding sections being of the cofunction type with windingsections of each layer separated by winding section voids, said voidsbeing characterized by the absence of active conductors, and whereinsaid first layer is superposed over said second layer so that eachwinding section on each layer is superposed with a corresponding windingsection void on the other layer, 1

insulating means securing said first and second layers together to forma composite layer wherein said first and third winding sections areinterdigitated with said second and fourth winding sections and whereineach of said first, second, third and fourth active conductors isdisposed in an array each terminating with one end in a first directionthereby forming a first margin on said layers and each terminating withan opposite end in an opposite second direction thereby forming a secondmargin on said layers, said member further including, first inactiveconductors for interconnecting said first winding sections along saidfirst margin on said first layer,

second inactive conductors for interconnecting said second windingsections along said second margin of said first layer, third inactiveconductors, superposed over said first inactive conductors, forinterconnecting said third winding sections along said first margin onsaid second layer,

fourth inactive conductors, superposed over said second inactiveconductors, for interconnecting said fourth winding sections along saidsecond margin on said second layer, and 7 means connecting said firstand third inactive conductors and means connecting said second andfourth inactive conductors so as to cause current in said first inactiveconductors to be opposite in direction to the current in said thirdinactive conductors, and so as to cause current in said second inactiveconductors to be opposite in direction to the current in said fourthinactive conductors whereby unwanted inductive fields from said firstand third inactive conductors tend to cancel and whereby unwantedinductive fields from said second and fourth inactive conductors tend tocancel.

7. In a position measuring transformer having a pair of relativelymovable transformer members,

one of said members comprising first and second layers,

each of said layers having interspaced first and second groups of activeconductors thereon, forming winding sections of first and of secondcofunction types wherein each layer includes winding section voids, saidvoids being characterized by the absence of active conductors, andwherein said first layer is superposed over said second layer so thateach winding section on each layer is superposed with a correspondingwinding section void on the other layer,

said active conductors extending at least substantially transversely ofthe direction of relative movement of said members, I

the groups of said first layer being interspaced with the groups of saidsecond layer to form an array,

means including first circuit conductors extending on one side of saidarray on each of said layers connecting said first groups on thecorresponding layer in a first series circuit, first connecting meansconnecting said first series circuit on said first layer to said firstseries circuit on said second layer, I

means including second circuit conductors on the opposite side. of saidarray on each of said layers connecting said second groups on thecorresponding layer in a series circuit, and

second connecting means connecting said second series circuit on saidfirst layer to said second series circuit on said second layer,

, 8. A transformer member according to claim 7 wherein said circuitconductors extend along said array and out of inductive couplingrelation to said active conductors.

9. A transformer member according to claim 8 wherein said activeconductors and said circuit conductors in each of said layers comprisecontinuous printed circuit elements.

10. A transformer member according to claim 7 wherein said first groupsform a first winding and said second groups form a second winding inquadrature relation to said first winding.

to carry current in a direction opposite to the current carried by saidfirst circuit conductors in said second layer and wherein said secondcircuit conductors in said first layer extend in inductive couplingrelation to said second circuit connectors in said second layer,

said second circuit connectors in said first layer being effective tocarry current in a direction opposite the current carried by said secondcircuit connectors in said second la er. 15 y 12. A transfonner memberaccording to claim 7 wherein said groups are spaced from each other ininterdigitized relation and are arranged in two similar patterns onopposite sides of a center line.

13. A transformer according to claim 7 wherein the terminal groups ofsaid array each comprises an active conductor in said first layer and anactive conductor in said second layer.

14. A transformer member according to claim 7 wherein the terminal groupat one end of said array comprises an active conductor in said firstlayer and an active conductor in said second layer,

said first conducting means connecting said last two mentioned activeconductors at adjacent ends thereof,

and wherein the terminal group at the opposite end of said arraycomprises an active conductor in said first layer and an activeconductor in said second layer,

said second conducting means connecting said last two mentioned activeconductors at adjacent ends thereof.

' 15. A position measuring transformer comprising relatively movabletransformer members, one of said members having windings of thecofunction type, each winding having a first portion thereof arranged ina first layer and a second portion juxtaposed therewith in a secondlayer, separate means for connecting the portions of each significancein series,

said first portions each comprising sections of active conductors havingmeans in said first layer connecting consecutive sections in series,

said second portions each comprising sections of active conductorshaving means in said second layer connecting consecutive sections inseries, said sections in said first and second layers being of the firstand second cofunction type, each of said layers having voids betweeneach of the sections, said voids having no active conductors therein,said first layer being superposed over said second layer so that eachwinding section on each layer is superposed with a corresponding windingsection void on the other layer,

another of said transformer members having a cofunction windinginductively related to said windings of.

16. A position measuring transformer comprising relatively movabletransformer members, one of said members having sine and cosine windingseach having a first portion thereof arranged in a first layer and asecond portion juxtaposed therewith in a second layer, separate meansfor connecting the sine portions and cosine portions, respectively, inseries,

said first sine and cosine winding portions each comprising staggeredsections of active conductors having means in said first layerconnecting consecutive sections in series, said second sine and cosinewinding portions each comprising staggered sections of active conductorshaving means in said second layer connecting consecutive sections inseries, each of said layers having voids between each of the sections,said voids having no active conductors therein, said first layer beingsuperposed over said second layer so that each winding section on eachlayer is superposed with a corresponding winding section void on theother layer,

another of said transformer members having a winding in- 7 ductivelyrelated to said sine and cosine windings.

17. A transformer according to claim 16, said sections of the sine andcosine winding portions of each layer having spaces juxtaposed with saidsections of the sine and cosine winding portions of the other layer.

18. A transformer according to claim 16, wherein consecutive sinesections and consecutive cosine sectionsof each layer are eachspacedapart providing spaces therebetween, each space juxtaposed withboth a sine section and a cosine section of the other layer.

19. A transformer according to claim 16, wherein consecutive sinesections of one layer are spaced apart providing a

1. A position measuring device comprising, a first relatively movable member including first and second layers of cofunction windings wherein each layer includes a substantially equal number of active conductors forming winding sections of first and of second cofunction types, wherein each layer includes winding sections separated by winding section voids, said voids in each layer being characterized by the absence of active conductors, and wherein said first layer is superposed over said second layer so that each winding section on each layer is superposed with a corresponding winding section void on the other layer, and a second relatively movable member having a winding electrically related to said cofunction windings.
 2. A winding member for a position measuring transformer comprising first and second layers of cofunction windings, each of said layers including a substantially equal number of active conductors, said active conductors forming winding sections of first and of second cofunction types, each of said layers including active conductors separated by active conductor voids, said voids in each layer characterized by the absence of active conductors, wherein said first layer is superposed over said second layer so that each winding section on each layer is superposed with a corresponding winding section void on the other layer.
 3. The member of claim 2 wherein at least some of said winding sections are formed with active conductors from each of said layers.
 4. The member of claim 2 wherein said active conductors are printed on an insulated layer and wherein said active conductors are connected into winding sections by printed inactive conductors.
 5. The member of claim 2 wherein the number of active conductors forming said winding sections of said first cofunction type equals the number of active conductors forming said winding sections of said second cofunction type.
 6. A winding member for a position measuring transformer comprising, a first layer having first active conductors connected to form first winding sections appearing substantiaLly at selected intervals of a first plurality of periodic intervals and having second active conductors connected to form second winding sections appearing substantially at selected intervals of a second plurality of periodic intervals, at least some of said first and second active conductors separated by active conductor voids, a second layer having third active conductors connected to form third winding sections appearing substantially at selected intervals of said first plurality of periodic intervals and having fourth active conductors connected to form fourth winding sections appearing substantially at selected intervals of said secondplurality of periodic intervals, at least some of said third and fourth active conductors separated by active conductor voids, said first, second, third, and fourth winding sections being of the cofunction type with winding sections of each layer separated by winding section voids, said voids being characterized by the absence of active conductors, and wherein said first layer is superposed over said second layer so that each winding section on each layer is superposed with a corresponding winding section void on the other layer, insulating means securing said first and second layers together to form a composite layer wherein said first and third winding sections are interdigitated with said second and fourth winding sections and wherein each of said first, second, third and fourth active conductors is disposed in an array each terminating with one end in a first direction thereby forming a first margin on said layers and each terminating with an opposite end in an opposite second direction thereby forming a second margin on said layers, said member further including, first inactive conductors for interconnecting said first winding sections along said first margin on said first layer, second inactive conductors for interconnecting said second winding sections along said second margin of said first layer, third inactive conductors, superposed over said first inactive conductors, for interconnecting said third winding sections along said first margin on said second layer, fourth inactive conductors, superposed over said second inactive conductors, for interconnecting said fourth winding sections along said second margin on said second layer, and means connecting said first and third inactive conductors and means connecting said second and fourth inactive conductors so as to cause current in said first inactive conductors to be opposite in direction to the current in said third inactive conductors, and so as to cause current in said second inactive conductors to be opposite in direction to the current in said fourth inactive conductors whereby unwanted inductive fields from said first and third inactive conductors tend to cancel and whereby unwanted inductive fields from said second and fourth inactive conductors tend to cancel.
 7. In a position measuring transformer having a pair of relatively movable transformer members, one of said members comprising first and second layers, each of said layers having interspaced first and second groups of active conductors thereon, forming winding sections of first and of second cofunction types wherein each layer includes winding section voids, said voids being characterized by the absence of active conductors, and wherein said first layer is superposed over said second layer so that each winding section on each layer is superposed with a corresponding winding section void on the other layer, said active conductors extending at least substantially transversely of the direction of relative movement of said members, the groups of said first layer being interspaced with the groups of said second layer to form an array, means including first circuit conductors extending on one side of said array on each of said layers connecting said first groups on the corresponding layer in a first series circuit, first connecting means connecting said first serIes circuit on said first layer to said first series circuit on said second layer, means including second circuit conductors on the opposite side of said array on each of said layers connecting said second groups on the corresponding layer in a series circuit, and second connecting means connecting said second series circuit on said first layer to said second series circuit on said second layer.
 8. A transformer member according to claim 7 wherein said circuit conductors extend along said array and out of inductive coupling relation to said active conductors.
 9. A transformer member according to claim 8 wherein said active conductors and said circuit conductors in each of said layers comprise continuous printed circuit elements.
 10. A transformer member according to claim 7 wherein said first groups form a first winding and said second groups form a second winding in quadrature relation to said first winding.
 11. A transformer member according to claim 7 wherein said first circuit conductors in said first layer extend in inductive coupling relation to said first circuit conductors in said second layer, said first circuit conductors in said first layer being effective to carry current in a direction opposite to the current carried by said first circuit conductors in said second layer and wherein said second circuit conductors in said first layer extend in inductive coupling relation to said second circuit connectors in said second layer, said second circuit connectors in said first layer being effective to carry current in a direction opposite the current carried by said second circuit connectors in said second layer.
 12. A transformer member according to claim 7 wherein said groups are spaced from each other in interdigitized relation and are arranged in two similar patterns on opposite sides of a center line.
 13. A transformer according to claim 7 wherein the terminal groups of said array each comprises an active conductor in said first layer and an active conductor in said second layer.
 14. A transformer member according to claim 7 wherein the terminal group at one end of said array comprises an active conductor in said first layer and an active conductor in said second layer, said first conducting means connecting said last two mentioned active conductors at adjacent ends thereof, and wherein the terminal group at the opposite end of said array comprises an active conductor in said first layer and an active conductor in said second layer, said second conducting means connecting said last two mentioned active conductors at adjacent ends thereof.
 15. A position measuring transformer comprising relatively movable transformer members, one of said members having windings of the cofunction type, each winding having a first portion thereof arranged in a first layer and a second portion juxtaposed therewith in a second layer, separate means for connecting the portions of each significance in series, said first portions each comprising sections of active conductors having means in said first layer connecting consecutive sections in series, said second portions each comprising sections of active conductors having means in said second layer connecting consecutive sections in series, said sections in said first and second layers being of the first and second cofunction type, each of said layers having voids between each of the sections, said voids having no active conductors therein, said first layer being superposed over said second layer so that each winding section on each layer is superposed with a corresponding winding section void on the other layer, another of said transformer members having a cofunction winding inductively related to said windings of.
 16. A position measuring transformer comprising relatively movable transformer members, one of said members having sine and cosine windings each having a first portion thereof arranged in a first layer and a second portion juxtaposed therewith in a second layer, separate means for connecting the sine portions and cosine portions, respectively, in series, said first sine and cosine winding portions each comprising staggered sections of active conductors having means in said first layer connecting consecutive sections in series, said second sine and cosine winding portions each comprising staggered sections of active conductors having means in said second layer connecting consecutive sections in series, each of said layers having voids between each of the sections, said voids having no active conductors therein, said first layer being superposed over said second layer so that each winding section on each layer is superposed with a corresponding winding section void on the other layer, another of said transformer members having a winding inductively related to said sine and cosine windings.
 17. A transformer according to claim 16, said sections of the sine and cosine winding portions of each layer having spaces juxtaposed with said sections of the sine and cosine winding portions of the other layer.
 18. A transformer according to claim 16, wherein consecutive sine sections and consecutive cosine sections of each layer are each spaced apart providing spaces therebetween, each space juxtaposed with both a sine section and a cosine section of the other layer.
 19. A transformer according to claim 16, wherein consecutive sine sections of one layer are spaced apart providing a space, one portion of said space containing a cosine section of that layer and another portion of said space being juxtaposed with both sine and cosine sections of the other layer, and wherein consecutive cosine sections of said one layer being spaced apart providing a space, one portion of said last-mentioned space containing a sine section of said one layer and another portion of said last-mentioned space being juxtaposed with both sine and cosine sections of said other layer. 